Alright... Well the story goes, a friend and I are doing boost leak tests on our cars... I have done plenty of boost leak tests, and I have now ran into an unheard of (to my knowledge) and an unsearchable occurance (who woulda thought)...

So, When doing the leak test, The boost gauge wont go past 2 psi on a 150 psi compressor... After hooking it all up, after about 3 seconds, the air being compressed leaks out of the exhaust noticeably... NOW, for the record:

1. I have never experienced this before, and ive parked my car and done boost leak tests at gas stations... i originally had the idea that since my tester was directly off of the turbo, that my wastegate was being opened from the air compressor blowing air directly and opening the wastegate and letting the air out of the exhaust...

2. Im not really trying to put both cars on jack stands and putting the car to TDC and playing with the boost leak then...

3. Ive done it on 2 Evos, one on stock cams, one with kelford 272's... i am stuck on this.. any help would be appreciated..


thanks

 

Is it opening the wg or is the wg loose at the flapper?

 

how can a boost leak test open the wastegate?
You are not pumping anything thru the exhaust

 

Sure everything is plumbed correctly on the car??

 

you definately don't have full grasp of how to do it or how things are connected around the engine then.
http://www.lancerregister.com/showthread.php?t=250611

 

opening the wastegate is going to be a function of air pressure on the diaphragm. the gate will open whether there is exhaust flow or not once you exceed the spring pressure on the actuator (that is unless the stock bcs defaults to closed when powered off, I'd be surprised if that was the case).

More likely, you've got a cylinder with partially open intake and exhaust valves.

 

my point is how can air get all the way down around the head/valves and then to the manifold/turbo to push the flapper open?

Yes, i will be on valves stuck open if anything as thats the only logical thing I can think of, but why would they be stuck open?
For the record I have never altered the crank position for a boost leak test, but I never thought to see if its leaking out my exhaust either. Just doesnt seek logical for me. I only really pay attention to the Intake manifold.

 

Don't want to thread jack, but is there a "how to" on boost leak testing? Is it as easy as just going off of the turbo inlet? Somone told me I will need to manually crank the engine till all valves are closed. Is the true?

 

i believe your supposed to check when the motor is at TDC thats what ive heard

 

The volume of air that a compressor delivers will EASILY go right through the turbine housing with or without an open waste gate. It probably won't even turn the wheel. If the valves are open It'll run right through and out the exhaust.

You need to make sure all the valves are closed, then do your thing.

 

How do you close the valves?

 

i wouldnt make this harder then it is.
Its a boost leak test not a compression test. if you are leaking out of the exhaust there is a valve open. I wouldnt even bother paying attention to anything past the Intake manifold with this test.

 

i'm mega surprised at how many ppl don't understand how to perform this test

 

. Yea If you not opening the throttle plate you need not even think to the valves. Your testing the charge pipes and boost lines. I still think something is hooked up incorrectly.

The motor has to be a TDC fo a boost leak test. HUH

 

before you post up something THIS retarded, the throttle plate doesnt need to be opened for air to get passed it... so if you are just shooting in the dark, youre an idiot and im going to start qupting all of you that try to even SOUND like you know what youre talking about... a boost leak test does more than the "charge pipes and boost lines"... FURTHER if you knew so damn much, you would know that even with the throttle closed that there are still ways for the air to go around... i.e. the t/b doesnt completely seal off the intake manifold... look whos laughing now... i asked for advice not silly amatuers posting about things they THINK they know...


now as far as the wastegate flapper goes, i dont know how it could be, only 2 psi of air pressure is making it into the system before the leak occurs... an opened valve COULD be it, and the wastegate COULD be it... i will have to do some more trials and error when i get home.. i just dont see how both of the evos are leaking out of the exhaust...


PLEASE no more attempted flaming posts... im not new to the evo world, nor do i care to hear about how uneducated you REALLY are...


thank you to those whom had decent ideas...